Posts Tagged: Robbin Thorp

A three-year study published Jan. 3 in the Proceedings of the National Academy of Sciences (PNAS) “uncovered major losses in the relative abundance of several bumble bee species and declines in their geographic range since record-keeping began in the late 1800s,” according to a University of Illinois press release.

The interdisciplinary study, led by Sydney Cameron of the Department of Entomology and Institute for Genomic Biology, University of Illinois, showed that "declining bumble bee populations have lower genetic diversity than bumble bee species with healthy populations and are more likely to be infected with Nosema bombi, an intracellular parasite known to afflict some species of bumble bees in Europe."

“The national analysis found that the relative abundances of four of the eight species analyzed have declined by as much as 96 percent and that their surveyed geographic ranges have shrunk by 23 to 87 percent,” according to the news release. “Some of these contractions have occurred in the last two decades.”

Cameron and his colleagues studied eight of the 50 species of bumble bees found in North America. Of the eight, four are significantly in trouble.

Said Cameron: "They could potentially recover; some of them might. But we only studied eight. This could be the tip of the iceberg.”

Of those western bumble bees, only B. occidentalis is in decline “and that one only in the western part of its range,” Thorp told us.

“Although the study treated B. pensylvanicus as the eastern species in decline, the researchers did not consider its very close western relative, B. sonorus, which used to be very common here and the rest of the Central Valley, but has virtually disappeared here since about 2003,” Thorp said.

"Both these species are doing well from the southern USA down into Mexico, however. This is a curious reversal of what one would expect if global warming might be a cause.”

Thorp has been tracking the now critically imperiled Franklin's bumble bee(Bombus franklini) since 1998. "It has the most restricted distribution range of any bumble bee in North America and possibly the world. Its range is about 190 miles north to south and 70 miles east to west in a narrow stretch between southern Oregon and northern California between the coast and Sierra-Cascade range,” he said.

Its known distribution includes Jackson, Douglas and Josephine counties in Oregon and Siskiyou and Trinity counties in California. It lives at elevations ranging from 540 feet in the north to 6800 feet in the south.

The decline, disappearance and possible demise of Franklin’s bumble bee, is closely linked to the widespread decline of native pollinators in North America, Thorp said, and should concern all facets of society. “The loss of a native pollinator could strike a devastating blow to the ecosystem, economy and food supply.”

Yellow-Faced Bumble Bee

YELLOW-FACED BUMBLE BEE, Bombus vosnesenskii, gathers nectar from a tower of jewels. The Cameron study looked at three species of western bumble bees, including this species. (Photo by Kathy Keatley Garvey)

Bombus Bifarius

BOMBUS BIFARIUS, shown here at Bodega Bay, was one of three western species of bumble bees looked at in the Cameron study. Of the three, only B. occidentalis is in decline “and that one only in the western part of its range,” Robbin Thorp said. (Photo by Kathy Keatley Garvey)

When this insect flashes by you in your garden, at first glance you think: "Yellow jacket? Paper wasp? What's that?"

Then it lands and you realize it's neither.

It's a bee.

The insects buzzing in our catmint last weekend were wool-carder bees, Anthidium manicatum (Linnaeus), as identified by several UC Davis entomologists: Tom Zavortink of the Bohart Museum of Entomology; native pollinator specialist Robbin Thorp, emeritus professor of entomology, and Lynn Kimsey, director of the Bohart Museum of Entomology.

Regarding the carder bee, Zavortink teamed with Sandra Shanks, then of the Bohart Museum, to write a scientific note, "Anthidium manicatum (Linnaeus) (Hymnoptera: Megachilidae in California)," published in the July 2008 edition of the journal Pan-Pacific Entomologist.

"The Palaearctic wool-carder bee Anthidium manicatum (Linnaeus, 1758) was introduced into New York state, presumably from Europe, before 1963 (Jaycox 1967)," Zavortink and Shanks wrote. However, it wasn't detected in California until much later. In 2007, an image of a carder bee from Sunnyvale, Santa Clara County, appeared on the Bug Guide website.

The name, carder bee, comes from its behavior of gathering "down" or "fuzz" from leaves to build its nest.

"Anthidium manicatum builds a linear row of cells, each one being lined and partitioned with cottony down 'carded' from hairy leaves," wrote Christopher O'Toole and Anthony Raw in their book, Bees of the World. "The term 'carder' refers to the teasing out or carding of woollen or cotton fiber with a comblike tool. The female of A. manicatum has five sharp teeth on each jaw and these are her carding tools."

The males are very territorial, the three UC Davis entomologists agreed.

Indeed they are.

The males, about the size of honey bees, buzzed furiously around the catmint last weekend. When they spotted an "intruder," such as a honey bee, they hit it with such force (body slam!) that the victim dropped to the ground.

We also observed carding of the leaves and mating. An Indy-500 male grabbed a female foraging on a catmint blossom.

Carpenter bees, which to the uninitiated look like bumble bees, are nice to have around the garden.

Maybe not so nice to have around your untreated patio or fences (as they drill holls in them to make their nests) but just think of them as pollinators, not pests.

As native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis, says: "Carpenter bees are beneficial in that they pollinate flowers in native plant communities and gardens. That far outweighs any damage to wood structures.”

We receive many calls and emails about carpenter bees. Many folks just want to know "what that loud buzz is" or "what's sharing our garden."

The other day we received an email from a carpenter bee enthusiast in Patterson who wanted to know how to keep attracting them to her garden.

Yes!

She inquired: "I had a couple of female bees (Xylocopa varipuncta) visit my garden this summer, but they seemed only interested in Salvia apiana and citrus flowers. Do you have any idea of other flowers that might interest them (I would like to keep them around longer)? Prefer California native plants."

Thorp responded: "Xylocopa varipuncta is a generalist flower visitor and has been recorded from a number of different kinds of flowers. Some natives you might consider include: Asclepias, Salvia, Trichostema, and Wislizenia for nectar; Eschscholzia and Lupinus for pollen.

In our yard, carpenter bees are partial to a variety of native and non-native plants, including salvia, lavender, catmint, rock purslane, purple oregano and African blue basil. They also like the golden day lilies and poppies.

"Franklin’s bumble bee has the smallest range of distribution of any of our 60 species of North American bumble bees, and perhaps of the 250 bumble bees in the world,” said noted bumble bee expert and native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis.

Thorp, who has been closely monitoring the Bombus franklini population since 1998, counted 100 that first year. In 2003, he found only three. And since 2006, only one.

Franklin's bumble bee may already be extinct, but he hopes not. Thorp and The Xerces Society for Invertebrate Conservation, headquartered in Portland, Ore., petitioned the U.S. Fish and Wildlife Service on June 23 to place it on the endangered species list.

A decision may be reached within 90 days.

“The decline of Franklin’s bumble bee is a signal that something is wrong in its environment,” said Thorp. “This is the canary-in-the-coal-mine measure.”

He hypothesizes that the key reason for its disappearance may be an exotic disease that spread from commercial bumble bee colonies to wild bumble bee populations.

“People often ask the value of Franklin’s bumble bee," said Thorp, a member of the California Academy of Sciences and The Xerces Society. "In terms of a direct contribution to the grand scale of human economies, perhaps not much, but no one has measured its contribution in those terms. However, in the grand scheme of our planet and its environmental values, I would say it is priceless.”

“Loss of a species, especially a pollinator, diminishes our global environment. Bumble bees provide an important ecological service--pollination. This service is critical to reproduction of a huge diversity of plants that in turn provide shelter, food (seeds, fruits) to diverse wildlife. The potential cascade of effects from the removal of even one localized pollinator may affect us directly and indirectly.”

Is it too late to provide protection for a species that may already be extinct?

No, it's not.

“Other species, especially plants and insects, thought to be extinct have reappeared after years of not being seen,” the UC Davis scientist said. “When populations of species are in decline, they may reach such low levels that they are not detected for several years in a row, despite intensive surveys--flying under the radar so to speak. It is my hope that this is the case with Franklin’s bumble bee.”

“One positive sign,” Thorp said, “comes from increasing finds the past two years of a related species, the Western bumble bee, which exhibited similar declines at the same time and places."

On his most recent trip, July 21-24, to the narrow distribution range, he didn't find Franklin's bumble bee but he did find the related Western bumble bee at two sites, one individual at each site.

That's a good sign. Perhaps B. franklini will eventually show up as well. Thorp is planning another trip in mid-August and another in early September.

Meanwhile, if the critically imperiled Franklin's bumble is granted protective status, a snowball effect could occur.

This could “stimulate research into the probable causes of its decline,” Thorp said. “This may not only lead to its recovery, but also help us better understand environmental threats to pollinators and how to prevent them in future. This petition also serves as a wake-up call to the importance of pollinators and the need to provide protections from the various threats to the health of their populations.”

NOTED bumble bee expert Robbin Thorp, shown here in his office at the Harry H. Laidlaw Jr. Honey Bee Research Facility at UC Davis, is on a mission to protect Franklin's bumble bee (Bombus franklini). His computer screen shows one of his images of the imperiled bumble bee. (Photo by Kathy Keatley Garvey)

Franklin's bumble bee

FRANKLIN'S BUMBLE BEE, pictured here on a California poppy, is mostly black. It has distinctive yellow markings on the front of its thorax and top of its head. It has a solid black abdomen with just a touch of white at the tip, and an inverted U-shaped design between its wing bases. (Photo by Robbin Thorp, UC Davis)

They're populating the sandy cliffs of Bodega Head, Sonoma County. A sure sign of their presence: dense clusters of turrets.

When they're not foraging among the wild radish (genus Raphanus), lupine (genus Lupinus) and other plants, these ground-dwelling bees are digging nests and rearing their young.

"The female sucks up fresh water from nearby, stores it in her crop--like honey bees store nectar--for transport to the nest," said native pollinator specialist Robbin Thorp, emeritus professor of entomology at the University of California, Davis.

"She regurgitates it on the sandstone, and excavates the moistened soil," he said. "She carries out the mud and makes the entrance turret with it."

The digger bees are sometimes referred to as "alternative pollinators," but they're all members of the Apidae family, which includes honey bees (the super pollinators), bumble bees, carpenter bees, sunflower bees, orchid bees, cuckoo bees and the like.

Digger Bees

DIGGER BEES head for their nests on a sandy cliff by Bodega Head, Sonoma County. The entrance turrets are easily seen here. (Photo by Kathy Keatley Garvey)